For purposes of this disclosure, the microwave region of the electromagnetic spectrum shall be considered to span the frequency range from approximately 1 GHz to beyond 100 GHz. As one can ascertain, modern microwave circuitry employs integrated circuits which essentially operate within the above-noted frequency range. As is well known, ordinary components such as semiconductors, integrated circuits, lumped components, connecting wires, and so on act very differently at microwave frequencies. Such frequencies are so high that a connecting wire or ribbon behaves as a parasitic complex impedance that undesirably affects circuit operation. For example, in microwave integrated circuits which may employ silicon or gallium arsenide structures, thin gold wires are commonly used for making electrical connections between the MIC substrates and also from the MIC substrates of the integrated circuits to monolithic integrated circuit devices or other circuit elements. These gold wires are generally attached to the gold plated lines on the substrates and to the gold pads on the monolithic integrated circuit devices by means of thermo-compression bonding, thermosonic bonding, or by some form of a welding process. The impedance of these connections is a known parasitic that degrades the high frequency performance of the circuit. Multiple wire connections are commonly made to reduce the parasitic impedance, but such connections are of questionable reliability, difficult to inspect and virtually impossible to pull-test. Gold ribbons or meshes of given width and size are sometimes used to establish an effectively wider, lower impedance conductor. However, such materials are very difficult to cut to the microscopic lengths involved and offer no width variation along their length. These ribbons or meshes are attached by the same means as the gold wires. As one can ascertain, the parasitic connection impedance of a wire, or constant width ribbon or a mesh becomes a performance limitation for high frequency, high performance microwave systems. Thus in order to circumvent the problem associated with a single wire, multiple wire connections are employed. Hence a first pad or terminal is connected to a second pad or terminal by the use of a plurality of wires all electrically in parallel and operating to reduce the adverse parasitic effects. Multiple wire connections are difficult to fabricate, difficult to inspect, and are virtually impossible to sample pull-test. The sample pull-test evaluates the mechanical strength of the connection and must meet certain minimum requirements for high reliability applications. Constant width ribbons or meshes are restricted by the smallest pad size of the attachment land areas and these jumpers, such as ribbons or meshes, are difficult to cut to a proper length. It is, of course, understood that the greater the length the more resistance and the more parasitic inductance and capacitance. Techniques have been used to compensate for the reactive portion of a single wire's impedance. Such techniques involve the utilization of parallel capacitance which in conjunction with the wire or ribbon inductance form a low pass filter which has a pass band impedance of 50 Ohms. This technique does not minimize the resistive portion of the parasitic impedance and requires very tedious and careful installation such as available with numerically controlled wire bonding machines. Extensive calibration of the bonder is demanded before bonding, in order to tune the wire loop so that is properly resonates with the capacitance. At higher microwave frequencies, such as those frequencies at the nd of the above-noted range this technique tens to become unmanageable because the corner frequency of the LC filter moves into the pass band. Moreover, the single wire loop is a gross mismatch in a modal sense, and even if the parasitic impedance is deemed to be low, mode switching can occur at the transition and crate all types of seemingly anomalous behavior at the system level.
A common technique used to offset these problems is to use multiple wire bonding. This technique has only recently been approved by the military at microwave frequencies and such approval is available in present MIL standards only for the microwave frequency range. These multiple wire connections approach an optimal electric connection but are extremely difficult to fabricate, inspect, and test. Additionally, repair work which may require a second bonding to the pad ranges from very difficult to impossible depending on the geometries o the bonding area and the number of wires installed. The ribbon or mesh connections are constrained in width by the smallest pad size and are difficult to cut to length. Tearing off the ribbon after bonding is a questionable practice in that it compromises the integrity of the bond. In general it can be said that handling ribbon or mesh in production environments is impractical.
It is therefore an object of the present invention to provide a method for forming a ribbon which permits the construction of optimally-shaped microwave integrated circuit connecting ribbons which avoid the above-noted problems. It is also the object of this invention to provide an effective means for storing and installing these ribbons into a microwave integrated circuit.